HttpServletRequest get JSON POST data

Question

I am HTTP POST-ing to URL http://laptop:8080/apollo/services/rpc?cmd=execute

with POST data

{ "jsondata" : "data" }

Http request has Content-Type of application/json; charset=UTF-8

How do I get the POST data (jsondata) from HttpServletRequest?

If I enumerate the request params, I can only see one param, which is "cmd", not the POST data.

Answer 1

Normaly you can GET and POST parameters in a servlet the same way:

request.getParameter("cmd");

But only if the POST data is encoded as key-value pairs of content type: "application/x-www-form-urlencoded" like when you use a standard HTML form.

If you use a different encoding schema for your post data, as in your case when you post a json data stream, you need to use a custom decoder that can process the raw datastream from:

BufferedReader reader = request.getReader();

Json post processing example (uses org.json package )

public void doPost(HttpServletRequest request, HttpServletResponse response)

  throws ServletException, IOException {

  StringBuffer jb = new StringBuffer();

  String line = null;

  try {

    BufferedReader reader = request.getReader();

    while ((line = reader.readLine()) != null)

      jb.append(line);

  } catch (Exception e) { /*report an error*/ }

  try {

    JSONObject jsonObject = HTTP.toJSONObject(jb.toString());

  } catch (JSONException e) {

    // crash and burn

    throw new IOException("Error parsing JSON request string");

  }

  // Work with the data using methods like...

  // int someInt = jsonObject.getInt("intParamName");

  // String someString = jsonObject.getString("stringParamName");

  // JSONObject nestedObj = jsonObject.getJSONObject("nestedObjName");

  // JSONArray arr = jsonObject.getJSONArray("arrayParamName");

  // etc...

}